Sound producing device



April 26, 1932. l.. A. KING 1,855,836

SOUND PRODUGING DEVICE Filed Nov. l, 1929 2 Sheets-Sheet 1 im mw i j! iunnmmlnm \.-1t14HNMM Niillhlllllll um v f \\f llllllllllllllillllllllApril 26, 1932. L. A. KlNG SOUND PRODUCING DEVICE 2 Sheets-Sheet 2 FiledNov @WMM Patented Apr. 26, 1932 UNITED STATES PATENT OFFICE A LAURENCEA. KING, 0F ST. CHARLES, ILLINGIS, ASSIG-NOR TO OPERADIO MANUFACTUR- INGCO., F ST. CHARLES, ILLINOIS, .A CORPORATION OF ILLINOIS Applicationfiled November The invention relates to sound producing devices, andmore particularly to loud speakers adapted to be employed in connectionwith sound amplifying devices.

VA loudspeaker embodying one form of the invention combines thedesirable feature of a speaker of the air-column type and anelectrodynamic speaker.

Air-column speakers of the usual design comprise reproducing unitshaving metal dia phragms and the air-column is generally of such lengththat it will reproduce fundamental frequencies between 50 and 70 cycles.Because of the tremendous power required to i5 drive the higherfrequencies through this aircolumn, the sound issuing from the mouth ofthe horn is distorted as the lower frequencies are predominant. Ofcourse, the advantages of an air-column horn are the fact that first thesound is concentrated and directed in a specific direction, and becauseof this the carrying power of the various frequencies which arereproduced are more or less equal; secondly, all of the energy comes outof the T95 mouth of the horn and is directed in the dif so frequenciesare between that and 100%. The

result is that at a distance feet away from the speaker, thereproduction begins to thin out and only certain frequencies reach oneunder normal intensity. Another disadvan- 5 tage of this type of speakeris the fact that there is just as much energy projected from the back ofthe speaker as from the front thereof, and this energy often tends tocreate very disagreeable acoustical effects. This is particularlynoticeable in theatre work 1, 1929. Serial No. 404,090.

where disagreeable acoustical effects are produced back-stage.

The improved loud speaker illustrated in the accompanying drawingspreferably employs an electro-dynamic cone type speaker in connectionwith an air-column horn, the diaphragm of the speaker being arranged inthe horn in such manner that the energy issuing from both the back andfront of the diaphragm is all projected from the mouth of the horn. Thearrangement is such that the walls of the horn function as a baiile, aswell as means for amplifying sound.

Many other objects and advantages wil-l appear as this descriptionprogresses, reference being had to the accompanying draw-k ings, whereinFigure 1 is a side elevation of a loudspeaker embodying the invention;

Fig. 2 is a front elevation of the improved speaker;

Fig. 3 is a plan elevation of the improved speaker;

Fig. 4 is a section taken on line 4--4 of Fig. 2;

F 5 is an enlarged section taken on line 5 5 of Fig. 2;

Fig. 6 is a rear elevation of a housing member forming part of theimproved speaker;

Fig. 7 is a side elevation of the housing member, shown in Fig. 6, and

Fig. 8 is a side elevation of one of a plurality of lbrackets attachedto the housing member, sho-wn in Figs. 6 and 7.

Referring to the drawings wherein I have llustrated an improved. form ofthe invenion embodied in aspeaker particularly adapted for theatre-work,the reference character 10 designates, generally, a horn which ispreferably molded from plastic material. The horn preferably comprises asubstantially eX- potential sound passage 11 which has its inner end 12arranged in the mouth 13 of the horn, the inlet end 12 being preferablyfrusto-conical in shape to accommodate a frusto-conical housing member15.

The horn 10 is preferably molded in one piece by employing a flexiblecore during the molding operation, but it is to be understood that myinvention is limited to such construction only to the extent indicatedin the appended claims. The housing member is preferably embedded in thehorn during the molding operation and preferably comprises a pluralityof outwardly extending flanges 17 arranged to project into the walls ofthe horn to rigidly secure the housing member to the horn. In additionto the out- Wardly extending flanges 17, I preferably provide aplurality of bracket members 18 around the outerV surface of the housingmember 15, the bracket members 18 being designed to embed themselves inthe Wall of the horn during the molding operation.

At its larger end, the housing member 15 is preferably provided with anoutwardly extending flange 20 to which are secured a plurality ofbracket members 21 comprising plates 23 and block-s 24. Each plate 23 isspotwelded to the flange 20 or secured thereto in any suitable manner.Secured to each plate 23 is one of the blocks 24, screws 26 and knurlednuts 27 being provided for this purpose (see Fig. 8). The knurled nuts27 are also embedded in the Walls of the horn during the moldingoperation and serve to secure the housing member 15 to the horn. Eachblock 24 is preferably provided with a screw-threaded hole 28 adapted toreceive one of a plurality of screws 29, whereby a loudspeaker 30 issecured to the housing member 15 and thus to the horn 10.

The loudspeaker 3() is preferably of the electro-dynamic type, andpreferably comprises a diaphragm 32 having a conical portion 33 whichhas its smaller end apertured to receive a sleeve 34, the sleeve 34being arranged to carry a Winding 35 which is generally referred to asthe voice coil winding and is adapted to be connected to the outputcircuit of a radio-receiving set, or the like.

The winding 35 is disposed concentrically in an annular magnetic field37 provided in an electro-magnet 38 which preferably comprises a centralpole piece 39 and an annular pole piece 40. The annular pole piece 40 isrigidly secured to a cup-shaped magnet member 42 having an aperture 43which accommodates one end of the pole piece 39. Preferably formedintegral with the cup-shaped magnet-member 42 are a plurality ofradially extending arms 46 which carry a ring 48 preferably formedintegral with the arms. It will be noted that the ring 48 is providedwith apertures 50 through which the screws 29 are passed when thespeaker 30 is secured to the blocks 24. Clamped between the ring 48 andthe blocks 24 is an annulus 52 which is offset, as at 53, to provide anannular groove 54. The annular groove 54 accommodates a pair of feltrings 55 and 56, between which an annular flange 58, preferably formedintegral with the conical portion 33, projects.

In the preferred form of the invention, the front end of the dynamicspeaker is prefer-V ably covered by a screen carried by an annularmember G1 secured to the ring 4S by the screws 29.

The terminals of the winding 35 are preferably connected by suitableconductors 63 to binding posts 64 carried by a bar G5 of insulationwhich is preferably rigidly secured to one of the arms 46. Suitableconductors 66 connect the binding posts 64 with the output circuit of aradio-receiving set, 0r the equivalent. The field winding 70 of theelectro-magnet 38 is connected by electrical conductors 81 to anysuitable source of direct current.

It will be noted that an annular passage.

73 is provided between the outer surface of the conical portion 33 andthe inner surface of the housing member 15, and that this passagecommunicates at its inner end With the inlet end of the sound passage11, the outer end of the passage 73 being closed. Obviously, sound wavesprojected from the outer or rear surface of the conical portion 33 willtraverse the sound passage 11 and will issue therefrom in substantiallythe same direction as the sound waves originating from the inner surfaceof the conical portion 33.

A feature of the invention is the employment of a dynamic speaker inwhich the electro-magnet or magnetizing structure is disposed in frontof the diaphragm 32 so that it is a relatively simple matter to have thespace around the outer or rear surface of the conical portion 33communicate with the inlet end of the sound passage.

The inner or front surface of the diaphragm 32 functions substantiallythe same way as the usual conical diaphragm provided in the ordinaryelectro-dynamic speaker, and, of course, the tones of higher frequenciesare projected directly from the mouth of the sound passage 11 in suchmanner that the carrying power of the dynamic speaker is fully utilizedas far as these higher tones are concerned. In addition, the soundsprojected from the back of the diaphragm 32 are unhindered andundistorted and are utilized to actuate and develop tones starting fromthe inlet end of the passage 11 to the mouth thereof. By thiscombination, all of the frequencies of the electro-dynamic cone speakerare projected from the mouth of the sound passage and the carrying powerof the electro-dynamic speaker is fully utilized. Of course, there maybe an out of phase condition existing to a certain extent, but due tothe use of the Walls of the horn as a baille, the out of phase conditioncannot be detected by the human ear.

Any suitable means may be provided for supporting the speaker horn 10,such, as for instance, a platform 75. In the preferred form of theinvention the horn 10 is provided with lugs 77 and 78 formed integralwith the Walls thereof and these lugs are adapted to rest upon thesupporting platform 7 5. A reinforcing rod 79 projects through the wallsof the horn, as best shown in Fig. 4.

If the field winding of the magnetizing structure is to be operated froma source of alternating current, I preferably provide suitablerectifying apparatus, as indicated at 80.

The speaker 30 is of such size that it has substantially the same volumeas loudspeakers of that type usually provided in radioreceiving sets,and the like. In other words, the speaker 3() is of such size so thatits volume is sufficient for a relatively large size room. Obviously,when the speaker 30 is combined with the horn 10 and the sound wavescoming from both sides of the diaphragm 32 are utilized, the volume ofsound issuing from the mouth 13 will be sufficient for theatre oroutdoor Work.

While I have illustrated and described a particular constructionembodying my invention, I do not wish to be understood as intending tolimit it thereto as the same may be variously modified and alteredWithout departing from the spirit of my invention.

W'hat I claim as new, and desire to secure by Letters Patent, is:

l. A device of the kind described comprising a horn having a soundpassage, a loudspeaker disposed at the mouth of said sound passage andprovided with a conical diaphragm, the outer side of said conicaldiaphragm being arranged to project sound into the inlet end of saidsound passage and the inner side of said diaphragm being arranged toproject sound away from said passage, said horn forming a baffle betweenthe two sides of said diaphragm.

2. A device of the kind described comprising a horn formed from plasticmaterial and provided with a sound passage, a housing member embedded inthe inlet end of said passage, a loud speaker secured to said housingmember and provided with a conical diaphragm, the outer side of saidconical diaphragm being arranged to project sound into the inlet end ofsaid sound passage and the inner side of said diaphragm being arrangedto project sound directly away from said sound passage.

3. A device of the kind described comprising a horn having a curvedsound passage, the inlet end of said sound passage being disposed in themouth thereof, a loud speaker embedded in said inlet end and providedwith a conical diaphragm, one side of said conical diaphragm adapted toproject sound into the inlet end of said sound passage and the innerside of said conical diaphragm being arranged to project sound directlyout of said mouth.

4. A device of the kind described comprising a horn having a soundpassage, the inlet end of the sound passage being disposed in the mouththereof, and a loud speaker mount-

